Calibration of a small size hexapod machine tool using coordinate measuring machine

Hexapod machine tool (HMT) is a device designed for micro milling; however, the deviations of the HMT's kinematic parameters due to manufacture and assembly errors can definitely affect its running accuracy. To identify the real kinematic parameters so as to improve the running accuracy of the HMT, a novel calibration test was performed on a bridge-type coordinate measuring machine. In the present research, a mathematical model was derived to present the relationship between pose errors and the errors of kinematic parameters of the HMT, the measurement method based on coordinate measuring machine was designed and a calibration experiment was carried out subsequently. The experimental results reveal that after calibration, both the position errors and orientation errors of the HMT decreased significantly, the symmetrical errors were improved as well. In addition, it is found that the running accuracy of the HMT is running direction dependent, which depends on the HTM's structures. The present research provides researchers with a new and effective calibration method to improve the running accuracy of HMTs.